The widespread deployment of heating, ventilation and air-conditioning (HVAC) systems has added significant flexibility to building design and form. It has provided indoor comfort even in severe climatic conditions and served to make habitable buildings with poor thermal performance. This flexibility has not, however, been without its costs. For example, in Australia, HVAC typically accounts for over 60% of energy use in commercial buildings [Australian Greenhouse Office, 1999], and is a substantial contributor to greenhouse gas emissions and is driving demand in the electricity network.
There is considerable research being carried out into optimal HVAC control strategies. These have considered aspects of comfort, electricity network interactions, and greenhouse gas emissions, though typically in isolation. For example, Braun et al. (1990, 2001) has investigated using building thermal mass for energy load shaping, Eto (2007) has demonstrated the use of air-conditioning to provide spinning reserve to the electricity network, Fanger (19617) pioneered research on thermal comfort, and the effects of thermal comfort on productivity have more recently been investigated by Seppänen et al. (2006). Greenhouse gas emissions have typically been achieved as part of overall energy savings strategies, though cogeneration systems (e.g. White and Ward (2006)) have directly exploited waste heat and fuel substitution to reduce emissions.
HVAC control systems typically use temperature as their control setpoint throughout a commercial building. The HVAC plant, including valve and damper positions, fan speeds, and so on are controlled in order to achieve a given setpoint temperature. Typically, this setpoint temperature is fixed, although state of the art HVAC systems may vary temperature based on a load shedding request.